Hydrothermal Synthesis, Structure, and Magnetic Properties of a Layered Fe(III) Carboxymethylphosphonate: [Fe(H2O)(O3P-CH2-CO2)] or MIL-49

[Fe^III(H₂O)(O₃P- (CH₂)-CO₂)] or MIL-49 was hydrothermally synthesized under autogenous pressure at 170°C for 48 h. Its bidimensional structure was solved from single-crystal X-ray diffraction in the monoclinic space group P2₁/c (No.14). Cell parameters are a =9.3836(3) Å, b=6.3798(3) Å, c=10.1371(3) Å, β=111.891(2)°, Z=4, and V=563.10(4) ų. Reliability factors of the structure refinement are R₁(F)=0.0470 and wR₂(F²)=0.1297 for 1036 reflections with I>2σ(I). The structure of MIL-49 is based on inorganic units built up from two edge-sharing [FeO₅(H₂O)] octahedra and two carboxymethylphosphonate groups. The connection of these units leads to the formation of hybrid sheets. A dangling oxygen atom from the carboxy function points toward the interlayer space and is responsible for hydrogen bonding with adjacent layers. Magnetic measurements and ⁵⁷Fe Mössbauer study reveal an antiferromagnetic ordering below T_N=25(1) K which becomes canted below 11(1) K.     

Dispirofluorene-indenofluorene derivatives as new building blocks for blue organic electroluminescent devices and electroactive polymers

A series of new dispiro[fluorene-9',6,9',12-indeno[1,2b]fluorenes] (DSF-IFs) has been synthesised. These new building blocks for blue-light-emitting devices and electroactive polymers combine indenofluorene (IF) and spirobifluorene (SBF) properties. We report here our synthetic investigations towards these new structures and their thermal, structural, photophysical and electrochemical properties. These properties have been compared to those of IF and SBF. We also report the anodic oxidation of DSF-IFs that leads to the formation of non-soluble transparent three-dimensional polymers. The structural and electrochemical behaviour of these polymers has been studied. The first application of these building blocks as new blue-light-emitting materials in organic light-emitting diodes (OLED) is also reported.     

Bioactive Seed Layer for Surface‐Confined Self‐Assembly of Peptides

The design and control of molecular systems that self‐assemble spontaneously and exclusively at or near an interface represents a real scientific challenge. We present here a new concept, an active seed layer that allows to overcome this challenge. It is based on enzyme‐assisted self‐assembly. An enzyme, alkaline phosphatase, which transforms an original peptide, Fmoc‐FFY(PO₄^2?), into an efficient gelation agent by dephosphorylation, is embedded in a polyelectrolyte multilayer and constitutes the “reaction motor”. A seed layer composed of a polyelectrolyte covalently modified by anchoring hydrogelator peptides constitutes the top of the multilayer. This layer is the nucleation site for the Fmoc‐FFY peptide self‐assembly. When such a film is brought in contact with a Fmoc‐FFY(PO₄^2?) solution, a nanofiber network starts to form almost instantaneously which extents up to several micrometers into the solution after several hours. We demonstrate that the active seed layer allows convenient control over the self‐assembly kinetics and the geometric features of the fiber network simply by changing its peptide density.     

Chiral N-Acetyl Selone-Promoted Aldol Reactions

The chiral oxazolidineselone functionality was found to be an excellent partner in the stereospecific acetate aldol reaction with aldehydes via the titanium enolates. Good stereocontrol was obtained as determined by NMR spectroscopy. The oxazolidineselone also provided a straightforward way to establish the stereopurity of the coupling reaction through ⁷⁷Se NMR spectroscopy.     

Efficient calculations of a large number of highly excited states for multiconfigurational wavefunctions

Electronically excited states play important roles in many chemical reactions and spectroscopic techniques. In quantum chemistry, a common technique to solve excited states is the multiroot Davidson algorithm, but it is not designed for processes like X-ray spectroscopy that involves hundreds of highly excited states. We show how the use of a restricted active space wavefunction together with a projection operator to remove low-lying electronic states offers an efficient way to reach single and double-core-hole states. Additionally, several improvements to the stability and efficiency of the configuration interaction (CI) algorithm for a large number of states are suggested. When applied to a series of transition metal complexes the new CI algorithm does not only resolve divergence issues but also leads to typical reduction in computational time by 70%, with the largest savings for small molecules and large active spaces. Together, the projection operator and the improved CI algorithm now make it possible to simulate a wide range of single- and two-photon spectroscopies. © 2019 Wiley Periodicals, Inc.     

Determining the solution state orientation of a Ti enolate via stable isotope labeling, NMR spectroscopy, and modeling studies

Our group has used Ti-promoted aldol additions with an oxazolidineselone as the chiral auxiliary with much success. In these reactions, the Se atom in the auxiliary both promotes stereospecific addition as well as reports on, through the use of 77Se NMR spectroscopy, the ratio of diastereomers produced and the geometry of intermediates as the reaction proceeds. Through stable isotope labeling and NMR spectroscopy, we are able to experimentally observe a Ti enolate in solution and gain insight into its structure and reactivity. Results from molecular modeling calculations are also presented for comparison with NMR data.     

Electrochemical Hydroboration of Alkynes

Herein we reported the electrochemical hydroboration of alkynes by using B₂Pin₂ as the boron source. This unprecedented reaction manifold was applied to a broad range of alkynes, giving the hydroboration products in good to excellent yields without the need of a metal catalyst or a hydride source. This transformation relied on the possible electrochemical oxidation of an in situ formed borate. This anodic oxidation performed in an undivided cell allowed the formation of a putative boryl radical, which reacted on the alkyne.     

Hierarchical Stable Enzyme Microenvironments for High‐Temperature Stability in Amine Solvents

Several methods have been proposed for capturing the CO₂ emitted into the atmosphere by human activity. To date, mainly amine‐based absorption processes are currently among the more promising systems for post‐combustion CO₂ capture. Tertiary amine solvents obviate the need for a high solvent regeneration temperature and fast absorption can be achieved with the use of carbonic anhydrase (CA), as an activator. In this study, the capacity of CA immobilization on nanoporous microparticles hierarchically structured to enhance their stability in tertiary amines is investigated. These microstructures allow for an efficient supply and presentation of substrate in the non‐aqueous solvent to the enzyme catalytic center and the particles' large size is attractive to make separation and reuse facile. These hierarchically structured particles conserve 70% of their initial activity after 30 d at 50 °C in amine solvent, whereas the free enzyme shows no activity after 1 h in the same conditions. In this work, we have overcome the technical hurdle linked to the recovery of the biocatalyst after operation thereby reducing costs of the system and importantly these micro‐bioparticles have shown a remarkable increase of the thermal stability of CA in an amine‐based CO₂ sequestration solvent as determined by a para‐nitrophenyl acetate assay.     

Investigation of the effect of pressure on retention of small molecules using reversed-phase ultra-high-pressure liquid chromatography

The effect of inlet pressure on the retention of a series of low molecular weight acids, bases and neutrals, was investigated at constant temperature in reversed-phase liquid chromatography using a commercial ultra-high-pressure system (Waters UPLC instrument). For neutral compounds, relatively small increases in retention factor of up to approximately 12% for a pressure increase of 500bar were noted; the largest values were obtained for polar solutes, or solutes of higher molecular weight. Ionisable acids and bases gave much larger increases in retention with pressure, in some cases as high as 50% for a pressure increase of 500bar. Thus, such compounds could show increases in retention factor approaching 100% over the pressure range available in the commercial UPLC instrument. Due to these differential increases, significant selectivity effects can be obtained for mixtures of different types of solute merely by changing the pressure.